1.Field of the Invention
The present invention relates to substrates coated with a stack of films including at least one film which reflects solar and/or infrared radiation.
The present invention also relates to the use of coated substrates for the production of panes specially adapted for thermal insulation and/or solar protection. These panes can be fitted into buildings, ships, and automobiles to reduce the amount of energy required to air condition the same.
2.Discussion of the Background
Stacks of thin films have previously been used to reflect solar and/or infrared radiation. Such films consist of one or more metallic films, such as silver films, alternating with films of dielectric material, such as metallic oxide films. These stacks are generally produced by successively depositing films onto the surface of a substrate using the cathodic sputtering technique under vacuum in a magnetic field.
Increasing the number of metal film layers in the stack enables the solar protection to be optimized, which in turn results in a reduction of the solar factor (SF) of the pane (the solar factor of a pane is the ratio of the total energy entering a room through the pane and the incident solar energy). However, increased metal film layers leads to a reduction in the transparency of the pane, which manifests itself in a decrease in the value of the light transmission T.sub.L of the pane.
U.S. Pat. No. 5,071,206 relates to a substrate on which is deposited a stack of layers made of three silver-based films alternating with four films of metallic oxide, such as indium oxide. The three silver films are substantially of equal thicknesses however, although the central silver film is slightly thicker than the other two. Unless such a substrate is incorporated into a laminated pane with the face of the substrate which has been coated with the film stack placed in contact with a thermoplastic intermediate film of, e.g., polyvinyl butyral (PVB), the reflective appearance of the substrate is not aesthetically pleasing. Instead, the substrate appears intensely reddish in reflection; a color that is not popular, especially with architects.
Clearly there exists a need for a stacked, thin film coated substrate having both high antisolar performance and high transparency, not forgetting the industrial feasibility of providing such a stack.